Method and system for mammalian joint resurfacing

ABSTRACT

A method and system for the creation or modification of the wear surface of orthopedic joints, involving the preparation and use of one or more partially or fully preformed and procured components, adapted for insertion and placement into the body and at the joint site. In a preferred embodiment, component(s) can be partially cured and generally formed ex vivo and further and further formed in vivo at the joint site to enhance conformance and improve long term performance. In another embodiment, a preformed balloon or composite material can be inserted into the joint site and filled with a flowable biomaterial in situ to conform to the joint site. In yet another embodiment, the preformed component(s) can be fully cured and formed ex vivo and optionally further fitted and secured at the joint site. Preformed components can be sufficiently pliant to permit insertion through a minimally invasive portal, yet resilient enough to substantially assume, or tend towards, the desired form in vivo with additional forming there as needed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of USapplication filed Apr. 12, 2002 and assigned U.S. Ser. No. 10/121,455,which is a continuation-in-part of US application filed Mar. 15, 2002and assigned U.S. Ser. No. 10/098,601, which is a continuation of aninternational patent application filed Aug. 28, 2001 and assigned SerialNo. PCT/US01/41908 which itself is a continuation-in-part of ProvisionalU.S. Application Serial No. 60/228,444, filed Aug. 28, 2000, the entiredisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] In one aspect, this invention relates to biomaterials formed exvivo for implantation and use within the body. In another aspect, theinvention relates to in situ curable biomaterials. In yet anotheraspect, this invention further relates to the field of orthopedicimplants and prostheses, and more particularly, for implantablematerials for use in orthopedic joints.

BACKGROUND OF THE INVENTION

[0003] Applicant has previously described, inter alia, prostheticimplants formed of biomaterials that can be delivered and finally curedin situ, e.g., using minimally invasive techniques. See for instance,U.S. Pat. Nos. 5,556,429, 5,795,353, 5,888,220, 6,079,868, 6,140,452,6,224,630 and 6,248,131 as well as published International ApplicationNos. WO 95/30388 and WO 97/26847 and International ApplicationPCT/US97/20874 filed Nov. 14, 1997 (the disclosures of each of which areincorporated herein by reference). Certain of these applicationsdescribe, inter alia, the formation of a prosthetic nucleus within anintervertebral disc by a method that includes, for instance, the stepsof inserting a collapsed mold apparatus (which in a preferred embodimentis described as a “balloon”) through a cannula that is itself positionedthrough an opening within the annulus, and filling the balloon with aflowable biomaterial that is adapted to finally cure in situ and providea permanent disc replacement. See also, Applicant's “Porous Biomaterialand Biopolymer Resurfacing System” (PCT/US99/10004), as well as“Implantable Tissue Repair Device (PCT/US99/11740), and “Static Mixer”(PCT/US99/04407) applications.

[0004] See also, U.S. Pat. No. 3,030,951 (Mandarino), U.S. Pat. No.4,203,444 (Bonnell et al.), U.S. Pat. No. 4,456,745 (Rajan), U.S. Pat.No. 4,463,141 (Robinson), U.S. Pat. No. 4,476,293 (Robinson), U.S. Pat.No. 4,477,604 (Oechsle, III), U.S. Pat. No. 4,647,643 (Zdrahala), U.S.Pat. No. 4,651,736 (Sanders), U.S. Pat. No. 4,722,948 (Sanderson), U.S.Pat. No. 4,743,632 (Marinovic et al.), U.S. Pat. No. 4,772,287 (Ray etal.), U.S. Pat. No. 4,808,691 (König et al.), U.S. Pat. No. 4,880,610(Constanz), U.S. Pat. No. 4,873,308 (Coury et al.), U.S. Pat. No.4,969,888 (Scholten et al.), U.S. Pat. No. 5,007,940 (Berg), U.S. Pat.No. 5,067,964 (Richmond et al.), U.S. Pat. No. 5,082,803 (Sumita), U.S.Pat. No. 5,108,404 (Scholten et al.), U.S. Pat. No. 5,109,077 (Wick),U.S. Pat. No. 5,143,942 (Brown), U.S. Pat. No. 5,166,115 (Brown), U.S.Pat. No. 5,254,662 (Szycher et al.), U.S. Pat. No. 5,278,201 (Dunn etal.), U.S. Pat. No. 5,525,418 (Hashimoto et al.), U.S. Pat. No.5,624,463 (Stone et al.), U.S. Pat. No. 6,206,927 (Fell), and EP 0 353936 (Cedar Surgical), EP 0 505 634 A1 (Kyocera Corporation), EP 0 521573 (Industrial Res.), and FR 2 639 823 (Garcia), WO 93/11723 (RegenCorporation), WO 9531946 (Milner), WO 9531948 (Kuslich).

[0005] Applicant's PCT Application No. PCT/US97/00457 (WO 9726847A1)includes the optional use of a mold, such as a balloon, and describesthe manner in which “[t]he mold created within the joint is preferablyof sufficient shape and dimensions to allow the resulting curedbiomaterial to replace or mimic the structure and function of theremoved fibrocartilage. The mold can be formed of synthetic and/ornatural materials, including those that are provided exogenously andthose provided by the remaining natural tissues. The mold can either beremoved from the site, upon curing of the biomaterial, or issufficiently biocompatible to allow it to remain in position.”

[0006] Applicant's later PCT Application No. PCT/US97/20874 (WO9820939A2) further describes the manner in which “‘mold’ will refer tothe portion or portions of an apparatus of the invention used toreceive, constrain, shape and/or retain a flowable biomaterial in thecourse of delivering and curing the biomaterial in situ. A mold mayinclude or rely upon natural tissues (such as the annular shell of anintervertebral disc) for at least a portion of its structure,conformation or function. The mold, in turn, is responsible, at least inpart, for determining the position and final dimensions of the curedprosthetic implant. As such, its dimensions and other physicalcharacteristics can be predetermined to provide an optimal combinationof such properties as the ability to be delivered to a site usingminimally invasive means, filled with biomaterial, and optionally, thenremain in place as or at the interface between cured biomaterial andnatural tissue. In a particularly preferred embodiment the mold materialcan itself become integral to the body of the cured biomaterial.”

[0007] Applicant's own use of such mold apparatuses to date hasconcentrated largely on the use of thin, extensible balloons adapted tobe positioned and then filled in situ with curable biomaterial, withparticular use as a replacement for the intervertebral disc followingmicrodiscetomy. In turn, there has been considerably less focus, todate, on the use of any such molds in other joints, such as the knee.FIGS. 6 and 7 of Applicant's PCT Publication No. WO 920939 A2, forinstance, shows a balloon and corresponding drilling template for use inknee surgery, the balloon having foot portions protruding from agenerally ovoid inflatable portion.

[0008] Finally, U.S. Pat. No. 6,206,927 describes a self-centeringmeniscal prosthesis device suitable for minimally invasive, surgicalimplantation into the cavity between a femoral condyle and thecorresponding tibial plateau is composed of a hard, high modulusmaterial shaped such that the contour of the device and the naturalarticulation of the knee exerts a restoring force on the free-floatingdevice. In what appears to be a related manner, Sulzer has introduced aunicompartmental interpositional spacer to treat osteoarthritis in theknee. See “Little Device Could Pack a Big Punch”, Sulzer Medica JournalEdition 2/2000(www.sulzermedica.com/media/smj-full-tex/2000/0002-full-text-6.html).The device is described as a metallic kidney-shaped insert which fillsin for the damaged cartilage between the femur and the tibia.

[0009] Such a metallic device, as described in either the Fell patentand/or Sulzer's product literature, is described as appropriate for usein younger patients with moderate to severe chondromalacia, particularlysince the product provides a hard, self-centering meniscal device thatis “devoid of physical means that fix its location”. In so doing, thedevice of Fell et al. tends to require a significant amount of intactcartilage and meniscus. Applicant's own products to date, includingthose improved embodiments described herein, have been largely gearedtoward more elderly patients, where such healthy cartilage is lacking.In turn, Applicant's devices tend to provide angular correction andimproved anchoring of the implant at the joint surface.

[0010] The recently issued Search Report in parent applicationPCT/US01/41908 includes two references, namely DE 19823325C1 and DE4339895 C1 directed to multipart devices that include portionsmechanically affixed to bone, and in turn, are unrelated to a polymericinterpositional device of the type presently claimed.

[0011] In spite of developments to date, there remains a need for ajoint prosthesis system that provides an optimal combination ofproperties such as ease of preparation and use, and performance withinthe body.

BRIEF DESCRIPTION OF THE DRAWING

[0012] In the Drawing:

[0013]FIG. 1 shows top and side perspectives of a preferred preformedknee implant prepared according to the present invention.

[0014]FIG. 2 shows an embodiment in which preformed components adaptedto be inserted and assembled in situ.

[0015]FIG. 3 shows an alternative embodiment in which preformedcomponents are employed.

[0016]FIGS. 4 and 5 show an embodiment in which a substantially open(saucer-shaped) mold is inserted into the joint site, to be filled witha corresponding curable biomateral in situ.

[0017]FIG. 6 shows a variety of alternative embodiments that include oneor more preformed component.

[0018]FIG. 7 shows a variety of alternative means for anchoring apreformed component such as that shown in FIG. 6d.

[0019]FIG. 8 shows a further variety for anchoring or stabilizing apreformed portion by the use of ancillary portions and/or surfacetexture.

[0020]FIG. 9 shows a variety of embodiments in a substantially closed(balloon like) mold is adapted to be inserted into the joint site andfilled with a corresponding curable biomaterial.

[0021]FIG. 10 shows a mold adapted for use as an acetabular mold inconnection with the replacement of the articulating surface in a hip.

[0022]FIG. 11 shows a patella femoral joint form suitable for use incombination with the method and system of this invention.

[0023]FIGS. 12 and 13 show various views of a particularly preferredknee implant of the present invention.

SUMMARY OF THE INVENTION

[0024] The present invention provides a method and system for thecreation or modification of the wear surface of orthopedic joints,including one or both of two articulating surfaces and/or portionsthereof, and particularly articulating joints such as the knee. In onepreferred embodiment, the method relies, at least in part, upon themanner in which the various stages of curing a curable biomaterial, andin turn, the various stages of forming a component from the cured orcuring biomaterial, can be correlated and optimized in a desired manner.In turn, such a method provides the ability to both generally andspecifically form the component for use in situ.

[0025] The present invention includes a variety of embodiments, each ofwhich preferably includes one or more components that are formed exvivo, and that are adapted to be inserted and finally formed orassembled in situ in order to provide a final prosthesis andarticulating joint surface. Examples of the various embodiments include,for instance,

[0026] 1) one or more components that are each at least partially, andoptionally completely, molded ex vivo, in a manner that permits thecomponent to be inserted, and optionally finally formed, in situ,

[0027] 2) a plurality of preformed components adapted to be assembled insitu, for instance in an overlapping or interlocking fashion,

[0028] 3) an insertable open (e.g., saucer shaped) mold, adapted to beinserted and positioned within the joint site, and there used incombination with a flowable biomaterial adapted to be delivered to theopen mold in situ, under conditions that permit the flowable biomaterialto cure in contact and/or combination with the mold in order to form afinal prosthesis,

[0029] 4) one or more generally extensible envelope (e.g., balloon-type)molds, adapted to be positioned and filled in situ with correspondingcurable biomaterials, one or more of the molds themselves providing oneor more regions of generally non-extensible, preformed material. In oneembodiment, for instance, a plurality of such envelope portions (e.g., abi-compartmental single envelope) can be adapted for use on both themedial and lateral tibial surfaces, respectively.

[0030] By the selection and use of a suitable biomaterial, and otherfeatures as described herein, the present invention provides an optimalcombination of benefits, as compared to methods previously described.Such benefits include those that arise in the course of preparation andstorage (e.g., sterility, storage stability), those that arise in thesurgical field itself (e.g., ease of use, adaptability, predictability),and those that arise in the course of long term use within the body(e.g., biocompatibility, moisture cure characteristics, tissue congruityand conformability, retention, wear characteristics, andphysical-mechanical properties).

[0031] In one preferred embodiment, the method and system involve thepreparation and use of partially or completely cured components that canbe formed outside the body, for insertion and placement into the body,and that can then be further formed within the joint site in order toenhance conformance. The optional ability to finally form one or morecomponents in situ provides various additional benefits, such asincreased control over the overall size and shape of the finalprosthesis, improved shape and compliance of the surface apposingnatural bone, and finally, improved shape and compliance of theopposite, articulating surface. The method and system permit the on sitepreparation or previous manufacture of a unicompartmentalinterpositional arthroplasty device from polymeric materials such aspolyurethane.

[0032] In a related and particularly preferred embodiment, the implantcan be prepared (including full cured) ex vivo, for later implantation.In a particularly preferred embodiment, as described below, the presentinvention therefore provides an implant that is designed to be formed toand congruent with the tibial surface, having a final femoral surfaceshape that serves largely as a glide path with respect to the femoralcondyle. Such a device can be used in patients having joints that haveprogressed to the stage of “bone on bone”, and thus provides areplacement for the function of articular cartilage as well as meniscus,and particularly at the central weight-bearing area, in order to restorealignment, providing an elastomeric, cushioning function. A preferredimplant of this type is also congruent with the tibial surface, basedupon both its initial shape, together with whatever final shaping mayoccur in situ. In turn, the present implant is more permanently anchoredin place, in significant part by one or more posterior projections, suchas the posterior lip shown in FIGS. 1, and 12-13 as well by the optionalbut preferred use of anterior fixation means (such as embedded sutures).

[0033] As shown in those Figures, such an embodiment includes a uniquecombination of a femoral glide path and convexity of the tibial surfaceof the implant, together with a posterior mesial lip. In turn, asprovided in the Figures and related description, the implant provides anindentation adapted to accommodate the tibial spine, which together witha slight feathering of the implant on the underside at the tibial spine,the general kidney shape of the implant, and the convexity of the tibialsurface, will permit the implant to be congruent with the concave tibiaand the posterior mesial lip that extends over the posterior portion ofthe tibia and into the mesial side of the tibia into the PCL fossa ofthe tibia. Importantly, such an implant can be provided in various sizesto accommodate different anterior-posterior dimensions of the tibia anddifferent tibial concavities. In other words, the amount of convexity ofthe tibial surface will be varied with the different sizes depending onthe amount of actual concavity that there is in the tibia.

[0034] As used herein, the word “cure”, and inflections thereof, willrefer to the extent to which a curable biomaterial, as used to form acomponent of this invention, has begun or completed whateverphysical-chemical reactions may be contemplated in the course of fullyforming the component, prior to or at the surgical site, for long termuse in situ. In turn, the biomaterial can be considered as uncured (asin component parts that have not yet been mixed or compositions thathave not yet been activated), or it can be partially cured (e.g.,wherein the components have been mixed, or compositions activated, underconditions suitable to begin the curing process), or it can be fullycured (e.g., in which case, whatever chemical reactions may haveoccurred have substantially subsided). Generally, uncured compositionsare sterile, storage stable, and often flowable, though are typicallynot yet formed or capable of being formed.

[0035] Curing compositions, by contrast, generally begin as flowablecompositions, but become nonflowable over a finite time period as theybegin to gel or set. Curing compositions can also be minimally formed,e.g., outside the body by the use of molds and/or suitable shapingtools, and/or within the body, as by the initial positioning of thecomponent on supporting bone and by the repositioning of opposing,articulating bone surfaces. Thereafter, it is contemplated and possiblethat some compositions of this invention can be further formed, overtime, as by the gradual effect of articulating bone in the course oflong term use.

[0036] As also used herein, the word “form”, and inflections andvariations thereof, will refer to the manner and extent to which acomponent has been sized and shaped, in either a general and/or specificmanner, for use at a joint site. In turn, the forming of such acomponent can occur either ex vivo and/or in vivo, as well as in ageneral manner (e.g., by the use of an ex vivo mold or tools) and/or aspecific manner (e.g., by final curing in apposition to supporting boneand/or opposing articulating bone surfaces), as well as combinationsthereof.

[0037] A component can be “specifically” formed in this manner in orderto conform the component (and particularly its surfaces) to thecorresponding specific shapes and dimensions of bone in situ, includingboth supporting bone surfaces and/or opposing (e.g., articulating) bonesurfaces. Such specific conformation, in turn, can be used to improve avariety of characteristics of the final implant, including comfort,mechanical performance, and/or long term stability. Such conformationcan also include aspects in which one or more components, or thecomposite prosthesis, are “conformed” in correspondence with the jointsite (e.g., by final shaping and curing processes that occur in situ).

[0038] Such conformation can also include aspects in which thecomponents, or prosthesis itself, are adapted to be “deformed” withinthe site, as by the application of force. For instance, a substantiallyfully formed component can be provided to have sufficient mechanicalproperties (e.g., strength and resilience) to permit it to be insertedinto a joint site and effectively deformed under normal anatomic forcesFor instance, a substantially convex component can be deformed to assumethe corresponding concave shape in situ, in, while retaining sufficientresilient strength to tend towards its original convex shape (e.g.,analogous to the manner in which a locking washer can be deformed inuse, while tending toward its original shape). Preferably, a final kneecomponent is adapted to be deformed under conditions of use within thebody (e.g., under physiologic load), while maintaining desired size andtibial congruency, and in a manner that provides desired fit andthickness for desired angular correction.

[0039] Hence a “preformed” component will generally refer to a componentthat is at least partially formed ex vivo, as by the surgeon's selectionand use of an appropriately sized ex vivo mold. Such a preformedcomponent can be specifically formed as well, including in an ex vivofashion, as by the use of a customized mold that is itself reflective ofthe particular dimensions and contours of the intended joint site. Suchcustomized molds can be prepared, for instance, by the use of externalimaging means, and/or by the appropriate use of negative and/or positivemolds taken at the tissue site. Optionally, and preferably, thepreformed component is specifically formed, in whole or in part, bybeing positioned in situ, prior to the completion of the curing process,and in apposition to both supporting bone and opposing bone surfaces.Once positioned within the joint site, any such component or prosthesiscan be adapted to be deformed in order to improve its retention and/orperformance in situ, e.g., resiliently deformed upon release ofdistracting forces and repositioning of the opposing bone surface.

[0040] For instance, a preformed composition is provided, formedinitially by the ex vivo onset of cure, in which the composition can beimplanted within on the order of 10 seconds to several days of the onsetof cure, preferably within about 30 seconds to about 10 minutes, andmore preferably within about one to about five minutes, whilemaintaining a surface exotherm of less than about 50C, and morepreferably less than about 45C once positioned within the body.

[0041] Once positioned in vivo, optional preferred preformed componentsof this invention are adapted to be finally shaped, for a period ofbetween about 10 seconds and one or more hours, and more preferablybetween about one minute and about five minutes. The lower limit isdefined largely by the time it takes to effectively reposition bone, orotherwise re-establish suitable force on the implant. The upper limit,in turn, is generally defined by the susceptibility of the implantedcomposition to further deformation or shaping. Such final shaping isgenerally accomplished, at least in part, under the force brought aboutby repositioning articulating bone surfaces. In one preferredembodiment, the partially cured composition is implanted underconditions that permit it to deform less than about 15%, preferably lessthan about 10%, and most preferably less than about 5%, underphysiologic forces, while maintaining tibial congruency and impartingdesired angular correction.

[0042] Hence, a particularly preferred preformed component of thisinvention can be implanted within an initial about one to about fiveminutes of the onset of its formation, and once implanted can be furthermolded or formed for a further period of about one to about fiveadditional minutes, in a manner that permits the resultant implant tosubstantially retain a desired final form and function.

[0043] The system of the present invention thereby provides the surgeonwith a variety of options, based on the manner in which these curing andforming processes are correlated. In one particularly preferredembodiment, for instance, the surgeon is provided with a compositionadapted to be partially cured and generally formed ex vivo, and thenpromptly inserted into the body and positioned at the joint site, whereit can be finally, and specifically, formed in the course of becomingfully cured.

[0044] By partially or fully curing the prosthesis ex vivo, the presentsystem simplifies the preparation process considerably, e.g., bylessening or avoiding potential problems (such as curing in the presenceof moisture, and surface exotherm in the presence of tissue) that canarise when a comparable composition is mixed and delivered to the jointsite while it is still flowable. Surprisingly, the present systempermits such prostheses to be not only formed, but also manipulated andinserted into the joint (e.g., through an incision of between about 1 cmand about 3 cm). Once inserted, the prosthesis can be positioned, andfurther formed in situ, all within a reasonable time frame. In fact, ithas been found that the procedure is amenable to outpatient use and evenregional anesthesia.

[0045] Moreover, the present system can avoid the use of such processesas the drilling anchor holes into the underlying bone, distraction ofthe knee joint, ligament release, leveling of the tibial plateau, andthe various other procedures typically involved with delivering thebiomaterial directly to the joint site in still flowable form. Yet, theprosthesis of the present invention provides a combination of propertiessuch as the extent of congruence with underlying bone, wearcharacteristics, fracture toughness, and avoidance of fibrillatedarticular cartilage, that meets or exceeds the combination of propertiesobtained using a comparable biomaterial in flowable form, delivered andlargely cured in situ.

[0046] In addition to its immediate use in such joints as the knee, thesystem of the present invention provides particular advantages whenapplied to ball and socket joints, such as the hip. In one suchembodiment, a balloon can be filled with a biomaterial as describedherein, and inserted and positioned within the acetabulum, prior to orfollowing filling, to provide a soft, conformable, durable lining forthe placement of a hip prosthetic portion. In a further embodiment, themethod and system involve the preparation and use of one or morepartially or fully cured component(s) formed outside the body, forinsertion and placement into the body and optionally further fitting andsecuring at the joint site. These preformed component(s) typicallyrequire less manipulation at the bedside and allow for alternativemethods of terminal sterilization, and final inspection and release atthe manufacturing site.

[0047] In a particularly preferred embodiment, the present inventiontherefore provides an implant that is designed to be formed to andcongruent with the tibial surface, having a final femoral surface shapethat serves largely as a glide path with respect to the femoral condyle.

[0048] This can be compared to other devices, such as that of the '927patent described above, which discloses a “self centering” device,formed entirely outside the body, and generally of a hard metal, byfirst determining the geometry of the entire knee compartment, includingboth the femoral and tibial surfaces. The device is designed to be veryhard, and based on such things as the concavity and convexity of varioussurfaces, which are designed to permit continued movement (translationaland rotational) and re-positioning of the device within the kneecompartment in the course of use. In turn, the device is permitted andexpected to continually move within the joint over the course of itsuse.

[0049] The present device can be used in patients having joints thathave progressed to the stage of “bone on bone”, and thus provides areplacement for the function of articular cartilage as well as meniscus,and particularly at the central weight-bearing area, in order to restorealignment. The implant provides an elastomeric, cushioning function, ascompared to the rigid and hard device of the '927 patent. The presentimplant is also congruent with the tibial surface, based upon both itsinitial shape and the final shaping that occurs in situ. In turn, thepresent implant is more permanently anchored in place, in significantpart by the posterior lip shown in FIGS. 1, and 12-13 as well by the useof anterior fixation means (such as embedded sutures).

[0050] Finally, the presently preferred implant has a peripheralthickness that is generally thinner than the thickness of their centralportion, and is positioned only partially within the knee compartment asdefined in the '927 patent, having a posterior lip that extends wellbeyond a compartment defined in that manner, and that serves a key rolein fixation.

DETAILED DESCRIPTION

[0051] The method and system (e.g., preformed component(s) and/orcurable biomaterial and mold) can be used to prepare a final prosthesis,in vivo, that provides a first major surface in apposition to andretained upon the supporting bone itself, and a second (generallysubstantially parallel and opposite) major surface adapted to provide awear surface for opposing (e.g., articulating) bone. By “retained upon”it is meant that the final prosthesis is maintained in a desiredposition upon the supporting bone surface in a manner suitable for itsintended use, e.g., by the use of one or more anchor points, by the useof adhesive or other suitable interface materials, by the use ofsutures, staples, and the like, and/or by a mechanical lock achieved bythe combination of a bone-contacting surface suitably conformed orconformable to the terrain of supporting bone, together with theretaining (and optionally including deforming) effect achieved uponrepositioning opposing articulating bone surface.

[0052] The first and second major surfaces can be provided in anysuitable manner, for instance, 1) by the preparation and insertion of asingle partially cured and generally preformed component into the joint,preferably under conditions that permit the component to become further,and specifically, formed in vivo, 2) by adding a flowable biomaterial toan initial preformed component (e.g., in the shape of a balloon or openmold) positioned at the tissue site, 3) by placing one or more fullycured and preformed components at the tissue site and optionally furtherfitting, adapting and/or securing the component(s) as needed, and/or 4)by assembling one or more preformed components in situ (e.g., side byside in an interlocking fashion upon the surface) such that theassembled components cooperate to provide the first and second majorsurfaces.

[0053] The system can therefore include modular implants, that includeone or more preformed components as described herein, in combinationwith one or more other (e.g., metallic) components. Any or all of suchcomponents can be made using materials having “shape memory” thatpermits the components to be easily inserted into the joint space, in amanner that permits the component(s) to assume or recover an alternativeshape upon the application of energy (e.g., heat slightly above bodytemperature). Optionally, such alternative shape can be achieved priorto insertion into the body. Alternatively, the molded in the bodyimplant can be taken out and reformed (e.g., by heat, radiation or othersuitable means) and reimplanted for final fit.

[0054] In addition to the partially or fully cured preformedcomponent(s) and/or curable biomaterial and related molds, the methodand system of this invention include the optional use of variousadditional materials and/or steps, e.g., to prepare the bone surfaceitself, to provide suitable interfaces (e.g., adhesive interfaces and/orprotrusions that can be further secured to the joint site or bysmoothing of the femoral condyle or tibial plateau as needed), to treatone or more surfaces in order to provide them with different or improvedproperties as compared to the inherent properties of the materialproviding the surface, and the like. Examples of such materials include,for instance, the use of adhesive materials, tissue in-growthstimulators, and fibrous materials (e.g., webs adapted to tether theimplant and/or to facilitate fibrous tissue ingrowth).

[0055] The partially or fully cured preformed component(s) canthemselves each provide uniform or non-uniform properties, and can beprovided in a plurality or range of styles and sizes. These componentscan be designed to conform to lateral or medial compartments, or both,and to right or left knees, or both. In a preferred embodiment, allembodiments can be inserted into the joint site in a minimally invasivefashion. By “minimally invasive”, in this context, it is meant that theprocedure of sizing, inserting, positioning and forming the prosthesis,in situ, can preferably be accomplished without the need for open,invasive incisions of the type conventionally used for inserting totalknee prostheses. In a preferred embodiment, the partially curedpreformed components can be further formed and fully cured in vivo toenhance compliance with the joint site.

[0056] The surface of the partially or fully cured preformedcomponent(s) can also be modified to provide any desired properties(e.g., promote adhesion), such as by the design and use of polymersthemselves or by surface treatment of the fully cured or curingembodiments to provide suitable reactive groups such as amines, hydroxylgroups, or other reactive or hydrogen bonding functionalities.Similarly, the partially cured preformed component or fully curedcomponent, including balloons or composite materials, can be providedwith appropriate surface coatings, e.g., biologically active agents topromote desired tissue interactions, including tissue or cellularadhesion, such as those selected from the group consisting of cytokines,hydroxyapatite, collagen, and combinations thereof. Such biologicallyactive agents can also include, for instance, anti-inflammatory agents,antitumor agents, antibiotics, complement inhibitors, cytokines, growthfactors, or inhibitors of growth factors and cytokines, as well ascombinations of any such biologically active agents with each otherand/or with adjuvants, and the like.

[0057] In one embodiment of this invention, partially cured, andgenerally preformed components are inserted into the joint site, andthere further and specifically formed to enhance compliance. In analternative embodiment, fully cured components in the shape of a balloonor open mold are employed to provide a final composite material byinserting the balloon or mold into the joint and there filling it with abiomaterial that cures in situ and conforms with the joint site. Inanother alternative embodiment, the fully cured component(s) areprovided and inserted into the joint either singly or piecemeal andoptionally further fitted and secured in vivo.

[0058] As an example of the first such embodiment, the inventionprovides an open ex vivo mold, adapted to approximate the desireddimensions of the joint site, and to receive a curable biomaterial. Asuitable mold can be formed, for instance, from the use of conventionalmaterials such as silicone materials, that permit the curing biomaterialcomponent to be easily and entirely removed at the desired time.Optionally, the mold can itself be provided with a coating or releaseliner, including those that can be integrated, in whole or in part, withthe component thus formed. Once the flowable biomaterial has beendelivered and partially cured in this ex vivo mold, and any optionalmolding or fabricating steps have occurred, the biomaterial can beremoved from the mold and inserted into the joint site, under conditionssuitable to permit it to be further and finally formed in vivo toenhance conformance with the joint site. Optionally, additional ex vivoforming steps or features can be performed, e.g., by imparting desiredcurvature and femoral glide paths, prior to inserting and final formingin vivo.

[0059] Also, in the course of molding the component ex vivo, and/ortransferring it to the tissue site, various structures and/or materialscan be incorporated into and/or onto the component itself, to enhanceits placement, retention and/or performance in situ. For instance, themold itself can be provided in a form sufficient to impart variousintegral structural features, such as tibial “tabs”, adapted to provideor improve the retention of the component at the tissue site. Such tabs,for instance, can be provided in the form of one or more protrusionsintegral with the mold itself and adapted to be positioned within and/oraffixed to the soft tissue and/or bone in vivo. Examples of such tabsare shown, for instance, in FIG. 1, where reference number 18 depicts araised posterior portion.

[0060] An insertable component can also be provided with one or moreancillary portions or protrusions formed of materials other than thatused to form the bulk of the component itself. For instance, sutures orfibrous materials can be incorporated into or onto the bulk material,for use in improving the initial and/or long term retention of thecomponent in situ, e.g, by tethering the prosthesis at the joint siteand in a desired position. Such other materials can be temporarilypositioned into or upon the mold itself, for instance, or otherwiseprovided, in a manner that permits them to become integrated into thebiomaterial as it fills the mold and becomes partially cured ex vivo.With the resulting component positioned in situ, the protrusions can beused to tether the implant, by securing them to the surrounding softtissue and/or bone by use of adhesives, sutures, screws, pins, staples,or the like, and other types of anchors, or combinations thereof, whichin turn can be prepared using bioabsorbable and/or non-bioabsorbablecements, composites, and adhesives. The materials can provide both animmediate fixation function, and optionally also a desired long termfunction, by permitting them to be either absorbed by the body overtime, and/or to permit or encourage fibrous tissue ingrowth for longterm fixation.

[0061] The reinforcing material can be provided in any suitable form,e.g., as fibers (e.g., sutures) or as a uniform woven or non-wovenfabric, optionally including one or more reinforcing fibers or layers. Asuitable non-woven fabric, for instance, is preferably a material suchas is commercially available under the trade name Trevira Spunbond fromHoechst Celanese Corporation. The non-woven fabric is generally composedof continuous thermoplastic fiber, needle punched together to yield afelt-like fabric. In addition to fabrics like Trevira Spunbond, othermaterials such as polyester staple mat, glass fiber mat, as well asother organic and inorganic fiber mats and fabrics can be employed.

[0062] Reinforcing fibers can be included within the woven or non-wovenfabric, or provided as separate layers of a composite. Such fiber layerscan preferably include a directional reinforcing fiber layer of organicor inorganic structural reinforcing fibers such as fiberglass, carbonfibers, aramid fibers which is available from DuPont Corporation underthe trade name Kevlar, linear polyethylene or polypropylene fibers suchas is commercially available from Allied-Signal, Inc. (now Honeywell)under the trade name Spectra, or polyester fibers. The phrase“reinforcing fiber” can include any fiber which, when used in its ownright or added to a composite fabric material, retains or enhancesdesired structural properties. The fibers can be randomly oriented, orpreferentially, they can be oriented in one or more directions. While anumber of specific types of materials have been given for use as thereinforcing fiber layer, it will be appreciated by those of ordinaryskill in the art that other equivalent-type reinforcing fiber layers canbe employed in the practice of the invention. A reinforcing fiber layercan be itself used to secure the prosthesis, or can be attached to awoven or non-woven fiber layer having a number of interstices or pores.Preferably, the reinforcing fiber layer and other fiber layers aresecured to each other mechanically, as by conventional stitching, needlepunching, stapling or buttons. In the case of certain applications,adhesives can also be used.

[0063] Similarly, a partially cured preformed component (and/orancillary portions incorporated therein) can also be provided withsuitable means to improve its ability to retain the component in situ,e.g., by the use of surface characteristics that provide improvedchemical interactions with the joint site. Such interactions can beachieved by the judicious use of bulk material compositions themselvesand/or the use of adhesives or other suitable interface materials. Thepartially cured, preformed, component can also be physically modified toincrease its interactions with joint site, as by surface roughening,etching or cross-hatching, which would tend to provide increased surfacearea, and in turn, improved mechanical retention. A partially cured,preformed, component can also be retained by external means that areotherwise secured to the surrounding bone and/or soft tissue by use ofadhesives, sutures, screws, pins, staples or the like or combinationsthereof. On the major surface opposing articulating bone, the partiallycured preformed component can be provided with suitable means as well,intended to improve or alter either its compliance and/or interactionswith the opposing bone surface.

[0064] In one particularly preferred embodiment, the system includes apartially cured preformed component that is first molded outside of thejoint site and adapted to be delivered to a tissue site and therepositioned in a fixed position. The mold can be of an open or closedconfiguration (and/or can involve a one- or multi-step molding process),adapted to preform one or both major surfaces, respectively. Oncepositioned, the partially cured component is adapted to be initially fitand positioned within the joint site, and to thereafter become betterconformed to the specific dimensions and/or terrain (e.g., anatomicstructure) of the joint site in vivo. Optionally, and preferably, themolds are designed to yield components that have optimum adhesion andconformance to the joint sites. The molds may also be heated during theex vivo partial curing process to optimize component properties or toprovide a component that is more formable in vivo.

[0065] In an alternative preferred embodiment, the method and systeminvolve the preparation and use of one or more fully or partially curedcomponent(s) formed outside the body, for insertion and placement intothe body and optionally further fitting and securing at the joint site.In one embodiment, the invention provides a single preformed componentthat is inserted into the joint site and optionally further fitted orsecured as needed. In another embodiment, the invention provides aplurality of preformed components, formed of the same or differentmaterials, and adapted to be delivered and positioned at the tissue sitein a manner that provides a final composite. The components can becombined at the site in any suitable fashion, e.g., by providing amechanical lock and/or by the use of interfacial materials such asadhesive layers. The components can be combined in any suitable fashion,e.g., as layers upon the bone, or as individual side-by-side componentsadapted to traverse the bone surface when combined. The use of preformedcomponent(s) can require less manipulation at the bedside and allow foralternative methods of terminal sterilization, and final inspection andrelease at the manufacturing site. The various means of retainingpartially cured preformed components, discussed herein, can be adaptedto work with fully cured preformed components.

[0066] The method and system of this invention can be used for repairinga variety of mammalian joints, including human joints selected from thegroup consisting of the tibial plateau of the knee, the acetabulum ofthe hip, the glenoid of the shoulder, the acromion process of theshoulder, the acromio-clavicular joint of the shoulder, the distaltibial surface of the ankle, the radial head of the elbow, the distalradius of the forearm, the proximal phalanx surface of the great toe,the proximal metacarpal surface of the thumb, and the trapezium of thewrist.

[0067] Those portions or combinations of preformed component(s) thatcontact the bone surface are preferably adapted to physically conformclosely to the prepared bone surface, e.g., to its macroscopic physicalcontours. Such conformation can be provided or enhanced in any suitablemanner, e.g., 1) by providing a partially cured preformed component thatis first made in an ex vivo mold and then adapted or modified to conformto the surface (e.g., by further forming in vivo), and/or 2) by use of apreformed balloon or composite mold material that is inserted into thejoint site and filled with a flowable biomaterial that cures in vivo sothat it conforms with the joint site and/or 3) by the use of fully curedpreformed component(s) that has optimum geometry for biomaterialcompliance once placed in the joint site and/or 4) by the preparationand use of a suitable (e.g., thin) interface material between bone andpreformed component (e.g., adhesive, filler, or cement material), and/or5) by the use of physical restraining means, such as adhesives, pins,staples screws, sutures or the like that are attached to protrusions inthe component itself or to an external means of securing it.

[0068] In yet other embodiments, the system of this invention caninclude the use of materials or markers (e.g., radiopaque) positionedwithin or upon the implant, to aid in visualization. e.g., usingfluoroscopy or other X-ray techniques.

[0069] The method and system of this invention will be further describedwith reference to the Drawing, wherein:

[0070]FIG. 1 shows a top and side perspective of a preferred preformedknee implant (10) prepared using an ex vivo mold according to thepresent invention. The implant provides a first major surface (12)adapted to be positioned upon the tibial surface, and a generally planarsecond major surface (14) adapted to be positioned against the femoralcondyle. In a typical embodiment, the second major surface, in turn, ispreferably provided with a femoral glide path (16) to facilitate itsperformance in situ, in the form of a generally central (e.g., oval)depression about 0.5 mm, or more preferably about 1 mm to about 5 mmdeep at its lowest point (2 mm as shown) and about 20 mm, and morepreferably about 30 mm to about 50 mm in length by 10 mm to 30 mm inwidth (40 mm by 20 mm as shown). Those skilled in the art, given thepresent description, will readily determine the actual dimensions foroptimal use, in both absolute and relative terms, depending on suchfactors as the actual joint size and desired results (e.g., angularcorrection). As shown, the implant is also provided with a tibialprojection (18), adapted to catch the posterior portion of the tibialplateau by extending over the rim of the tibial plateau distally. Thebody of the implant can have dimensions on the order of between about 35mm, and preferably about 40 mm to about 60 mm in the anterior-posteriordimension, between about 20 mm, and preferably 30 mm to about 35 mm, oreven about 40 mm in the medial-lateral dimension, and a maximumthickness (at the posterior lip of between about 8 mm, more preferablyabout 10 mm, and about 20 mm, or about 2 mm to about 4 mm (e.g., 3 mm)greater than the thickness of the implant at the center. As a result, itcan be seen that fixation is accomplished by effectively capping thetibial plateau with one or more projections extending distally over therim of the plateau.

[0071]FIG. 2 shows an embodiments in which a plurality of preformedcomponents are adapted to be inserted and assembled in situ to providethe final implant (20) FIG. 2a shows an embodiment, in which preformedcomponents (22 through 25, respectively) are assembled in a side-by-sidemanner sequentially, and in situ, and upon the tibial surface. Thematable preformed sections each provide at least a portion of theresultant bone-contacting surface and wear surface, as well as one ormore portions adapted to provide a mechanical lock with one or morerespective other portions. The mechanical lock can be achieved in anysuitable manner, as by the provision of corresponding male and femaleportions, respectively. The portions can be mated, in situ, e.g., in apress fit or sliding manner, in order to attach the respectivecomponents. As can be seen in the raised perspective of the sameembodiment, and FIG. 2b, in the resultant assembly, the combinedcomponents cooperate to provide both a tibial bone-contacting surface(28) and a wear surface (26).

[0072] In the alternative embodiment of FIG. 3, rather than beingpositioned in a side-by-side fashion across the bone surface (as in FIG.2), a final implant is provided using interlocking preformed components(show in this case as portions 31 through 33, respectively) are insteadprovided in a form that permits them to be stacked upon each other,e.g., by layering or sliding them onto each other, and positioned uponthe surface, in situ. The portions can be assembled in any suitablefashion, e.g., entirely on the tissue site, entirely ex vivo, or invarying combinations as desired. Optionally, and preferably, thegenerally planar portions are provided with corresponding matableportions, e.g., in the form of grooves and tabs to provide a slidingfit, or a depression and corresponding projection to provide either apress fit, snap fit, or other suitable fit sufficient to prevent lateraldisplacement to the extent desired. The resultant formed prostheticimplant can be provided with various features as described herein,including desired molded portions adapted to provide better fit orperformance. Top portion (31) is particularly well suited to provide adesirable wear surface, while one or more intermediate portions (asshown by element 32) are adapted to provide an optimal combination ofsuch properties as thickness, cushioning, and angular correction. Asshown the lowermost portion (33) is shown with a projection (34) adaptedto be retained within a corresponding anchor hole or suitable depressionformed into the bone itself. FIGS. 3b and 3 c provide generally bottomand top views, respectively, showing the manner in which the portionscan be combined in a layered fashion.

[0073] In the embodiment of FIG. 3, preformed layers are shown havingprotrusions adapted to be positioned in a corresponding indentationwithin each underlying layer (or bone), in order to form a compactstack. In such an embodiment, the corresponding system will typicallyinclude at least two preformed components, including the initial,bone-contacting component, and final component providing the wearsurface. The system can provide one or more intermediate layers, e.g.,the number and/or selection of which can be used to provide a finaldesired height to the overall composite, and/or to provide differingproperties (e.g., with respect to compressibility, resilience, tissueingrowth), and/or to provide improved retention between the first andfinal components.

[0074]FIG. 4a shows an embodiment in which a substantially open(saucer-shaped) mold (40) is inserted into the joint site, to be filledwith a corresponding curable biomateral in situ. The top (42) of themold is open to receive biomaterial (not show), while the bottom (44)provides a lower major surface (46) adapted to contact bone andterminates in a filled protrusion (48) adapted to be positioned within acorresponding anchor point drilled in the bone itself. The anterior edge(50) of the cup is substantially perpendicular to the plane of the cupitself, while the posterior edge (52) is tapered (and optionally raised)to accommodate the corresponding shape of the tibial spine.

[0075] As shown, and for use in an adult human, the ex vivo moldaccommodates a predetermined volume of biomaterial of on the order ofabout 5 ml to about 15 ml. As a further advantage of this invention, theamount of biomaterial actually can be predetermined and controlled tocorrespond with the ex vivo mold volume. In addition the ex vivo moldsare designed for optimum sizing and conformance to the joint site andMRI software may be used to chose best mold for joint site. Implantthickness and hence angular correction can be controlled in this way.

[0076]FIG. 4b shows a bottom perspective view of the mold apparatus ofFIG. 4a, showing the filled protrusion (48). The posterior edge portion(and particularly the posterior mesial edge portion, as seen in thefigure) can be seen as provided with a groove or indentation (54), againto accommodate the typical shape of the corresponding tibial spine.Overall, the mold can be seen as assuming a generally kidney-shapedconfiguration, adapted to correspond with the tibial surface. Such amold can be provided in a plurality of sizes, and shapes, to be selectedat the time of use to accommodate the particular patient's needs andsurgeon's desires.

[0077]FIGS. 5a and 5 b show the mold of FIG. 4a being positioned upon atibial surface (FIG. 5a), with the protrusion positioned within acorresponding anchor point, and (in FIG. 5b) with the tip of abiomaterial delivery cannula (56) positioned upon it, and with flowablebiomaterial (58) being shown in the course of delivery.

[0078]FIG. 6 shows a variety of alternative embodiments that include oneor more preformed component. FIG. 6a shows a simple wedge shapedembodiment (60), in which the posterior portion (62) is significantlyincreased in size as compared to the anterior (64). FIG. 6b shows animplant (66) molded to provide portions (here, layers) having differingwear characteristics, including a preformed top having improved wear ascompared to the separately formed bottom portion (70). FIG. 6c, bycomparison, shows a plurality of components (72) adapted to bepositioned and assembled in situ at the time of surgery. These includean upper portion (74) having improved wear characteristics as comparedto the others, a bottom portion (78) being suitably formed to thepatient's geometry and desired angular correction, and one (or more)central portions (76) adapted to be positioned between the top andbottom portions to achieve desired properties such as overall thickness,angles, and/or physical chemical properties (such as moduli).

[0079] The embodiment of FIG. 6d shows a single piece (80) as might becut from preformed material at the time of surgery, while FIG. 7 shows avariety of alternative means for anchoring a preformed component such asthat shown in FIG. 6d. These include the use of a grout (82) or othersuitable interface material as shown in FIG. 7a; the use of a separateexternal retaining device (84) as shown in FIG. 7b; the use ofexternally provided pins, screws, sutures, etc. as exemplified byelements (86) which generally traverse the body itself as in FIG. 7c;and the use of one or more anchor portions (88) positioned along one ormore suitable surfaces as shown in FIG. 7d.

[0080]FIG. 8 shows a further variety for anchoring or stabilizing apreformed portion by the use of ancillary portions and/or surfacetexture, including a roughened surface (90) as in FIG. 8a; or tabs(e.g., provided by fabric or suture like materials) as shown as elements92 and 94 of FIGS. 8b and 8 c, respectively. The surface texture caninclude, for instance, a dimpled or other suitably textured surface toimprove lubricity. In a preferred embodiment, the texture would besufficient to allow entrapment of lubricant under no load or low loads,followed by obliteration of the pattern with load. In yet anotheralternative embodiment, a femoral forming device of the type describedin Applicant's previous U.S. Provisional Application Serial No.0/341,070 can be used to impart a textured surface. In practice, thepreformed components can benefit from any suitable combination of thevarious features and embodiments described or shown herein.

[0081]FIG. 9 shows a variety of embodiments in a substantially closed(balloon like) mold is adapted to be inserted into the joint site andfilled with a corresponding curable biomaterial, the mold itselfproviding a preformed articulating wear surface, including FIG. 9a whichshows an inflatable balloon portion (96) that includes an integralpreformed wear surface and portion (98), as well as a lumen (100)adapted to fill the inflatable portion with flowable biomaterial. FIG.9b shows a corresponding balloon (102) though without a preformedportion, and including its biomaterial lumen (104). Although not shown,the balloon of this or any embodiment can include various interiorand/or exterior surface coatings, and can have regions and/or layershaving different desired physical-chemical properties (such asporosity). FIG. 9c shows a bi-compartmental closed balloon-like mold(106), wherein each compartment is adapted to conform to a respectivemedial or lateral tibial surface.

[0082]FIG. 10 shows a mold adapted for use as an acetabular mold (110)in connection with the replacement of the articulating surface in a hip,when filled with biomaterial, the mold forming a concave portion adaptedto retain a corresponding femoral head. The mold is shown providing athin generally cup-shaped mold adapted to be filled in any suitable form(e.g., using a removable conduit (not shown) attached to the spacebetween inner and outer sealed layers (116 and 114, respectively)forming the mold.

[0083]FIG. 11 shows a patella-femoral joint form suitable for use incombination with the method and system of this invention. As shown inthe views of 11 a through 11 c, the form includes a silicone or othersuitable pad material (122) having aluminum or other suitable stayportions (124) and terminal handle or grasping portions (126). In use,with the knee at a generally 45 degree angle, the piece is formed to thefemoral bone surface, with its form maintained by bending the aluminumstays. With anchor points cut into the femoral bone, if desired, theform is held tight against the bone with the upper handle held away frombone to permit the delivery of curable biopolymer between the form andthe bone. As polymer is placed onto the bone (and into any anchorpoints) the form is maintained for a time sufficient to suitably formthe polymer, whereafter it can be removed.

[0084]FIG. 12 shows various views of a particularly preferred implant ofthe present invention, of the general type shown in FIG. 1 and describedabove, including a top plan view (a), front plan view (b), side planview (c), section view (d) taken along A-A of FIG. 12(a) and a sectionview (e) taken along C-C of FIG. 12(a). FIG. 13, in turn, show side byside top plan views (a) and (b) of corresponding implants for the leftand right knees, respectively. Reference numbers for the variousportions correspond to those described in FIG. 1, including preformedknee implant (10), the first major surface (12) adapted to be positionedupon the tibial surface, and a generally planar second major surface(14) adapted to be positioned against the femoral condyle. The secondmajor surface is shown having a femoral glide path surface (16) tofacilitate its performance in situ, adapted to form a generally centraldepression having the dimensions described herein. The glide path isfully formed in situ, by a suitable combination of both shaping andrepositioning of the femoral condyle in the manner described herein.

[0085] An implant of the type shown provides various benefits, includingthe correction of varus deformities, based in significant part upon thepresence and configuration of the posterior mesial lip (18), and thecutout (kidney bean shaped) for the intercondylar eminence (see FIG. 4b,ref 54). The tibial projection (18) is adapted to catch the posteriorportion of the tibial plateau. The implant itself has dimensions asprovided herein, and can be provided using one of a collection of moldsof multiple sizes and/or styles in accordance with the variousparameters of the present invention. A kit can be provided containingmolds of various sizes, e.g., varying by 1 mm or 2 mm increments inthickness and providing a range of anterior to posterior dimensions.Such molds can also be used to provide implants having bottoms ofvarious shapes, e.g., either a flat or curved bottom, and for either theleft or right knee.

[0086] An implant such as the configuration shown in FIG. 12 ispreferably used in a method that includes first determining the properimplant thickness needed to match physiological valgus. The surgeonprepares the site arthroscopically, removing excess cartilage andremoving the medial meniscus to the medial ring, using a portal of about1 cm in order to provide suitable arthroseopic access while maintainingthe presence of fluid in the joint. The implant can be initially moldedex vivo, using a mold selected from those available and including one ormore embedded or attached fixation portions (e.g., anterior sutures ortabs), at which time it is inserted into the knee. The surgeon will thentypically feel the implant once in position, to confirm that the implantis properly seated, and will extend the knee to provide varus stress onthe lower leg, obtaining congruency as the implant continues to cure byfinally molding both surfaces of the implant (to both the tibial surfaceand condyle, respectively).

[0087] Optionally, and preferably, the surgeon can also use a femoralforming device (e.g., spoon-shaped device) of the type described incopending US Provisional Application mailed Dec. 7, 2001 and entitled“Method and Device for Smoothing The Surface of Bone in an ArticulatingJoint”, the disclosure of which is incorporated herein by reference, inorder to prepare a femoral glide path and remove unwanted undulations.After a suitable time, e.g., about 1 to about 5 minutes, and typicallyat about 2 minutes using presently preferred polyurethane compositions,the implant can be sutured to the anterior rim, and the knee can beflexed to obtain complete range. Optionally, during or following thisprocedure, the joint can be filled with a suitable fluid and visualized,after which the knee is extended and braced, with the access portal(s)closed by suitable means (e.g., sutured).

[0088] As described in Applicant's co-pending U.S. provisionalapplication No. 60/228,444, the present application describes a methodand system for the creation or modification of the wear surface using animplanted material fixed to the support structure of the original wearsurface, to generally conform to the shape of the original surface in amammal. A method or system where the end of the bony surface is arotating, sliding or rolling surface, such as in the knee, finger, hip,toe, spine, wrist, elbow, shoulder, ankle, or TMJ joint. The implantwill function:

[0089] a) as a spacer,

[0090] b) as an impact absorber

[0091] c) as a surface with improved coefficient of friction (ascompared to the diseased surface), and/or

[0092] d) to increase the weight bearing area and improve congruency ofthe joint surface (as compared to the diseased condition).

[0093] The method and system of this invention can be applied to areasof aseptic necrosis, such as the nevecular bone in the wrist. Thematerial to be implanted consists of a plurality of materials, such aspolymers, including polyurethane, polyethyelenes, polyureas,polyacrylates, polyurethane acrylates, hydrogels, epoxies and/or hybridsof any of the above.

[0094] In an alternative embodiment, the surface can be provided by anyof a series of metals, including titanium, stainless steel, cobaltchrome millithium alloys and tantalum. Other surface materials caninclude various ceramics and biologic polymers.

[0095] The implantable material for the resurfacing can be formed exvivo and/or in vivo as an injectable material that sets up to the moldedshape. The methods for changing state from liquid to solid state includecooling or heating, the passage of time, which allows for a change ofstate, or a chemical reaction between different reactants. The reactioncan be exothermic or endothermic. The set-up can be light activated orchemically catalyzed or it could be heat activated. Examples of suchsystems include flowable polymers of two or more components, lightactivated polymers, and polymers cured either by catalysts or by heat,including body heat, or any suitable combination thereof. Molds can beused in the form of balloons, dams or retainers. They can be used incombination with the local anatomy to produce the desired shape andgeometry. Molds can be of materials that are retained and becomes partof the implant or could be removed after curing of the biomaterialcomponent.

[0096] In an alternative embodiment, the material would be semi-solidand could be shaped and then set up in vivo. This would allow for theminimally invasive application, either through an arthroscopic portal orthrough a small mini arthrotomy. As a further embodiment, the materialcould be synthesized ex vivo and then machined to fit using imaging topre-determine the desired geometry and size of the implant. As a furtheralternative, a range of implant sizes could be provided and sizing couldbe accomplished during the procedure. An ex vivo mold could be fit usingmolding materials and the implant could be molded on site just prior toimplantation.

[0097] Fixation methods for the implant would include biologic glues toglue the implant to the underlying surface, trapping of the implant intoa cavity on the surface that causes a mechanical lock, using variousanchors to the underlying structure and fixing the implant to thatsurface or using mold retainers and/or screws, staples, sutures or pins.In alternative embodiment, anchors in the underlying structure may beused for fixing the implant to that surface and we may also use a tissueingrowth system to secure anchoring.

[0098] In the preferred embodiment, the patient will have a diagnosis ofosteoarthritis and have loss of cartilage on the articulating surface. Adetermination will be made of the amount of correction needed for thereestablishment of a normal angle of articulation. The ligaments will bebalanced so that there is no loss of range of motion with the implant inplace and the surface will be placed in such a position that theeventual resulting surface geometry reestablishes the same plane andorientation of the original articular surface.

[0099] Access to the site is obtained in a minimally invasive way. In apreferred embodiment, this is accomplished through arthroscopic meanswith arthroscopic portals. In an alternative embodiment, the access isaccomplished by a mini arthrotomy with a small incision that allowsaccess to the joint without sacrificing nerves, vessels, muscles orligaments surrounding the joint. In the preferred embodiment fibrillatedarticulating cartilage that is degenerated is removed down to thesubchondral surface. The surface is dried and prepared for appropriateanchoring. This may include anchor points that give a mechanical lock orthat alternatively simply supply horizontal and lateral stability. Thesurface may be prepared by drying and roughening in case a tissueadhesive is used. Pre-made anchors may be installed. These may be madeof various metallic materials or of polymers and may consist of pegsthat would extend up through the implant to anchor it to the underlyingsurface. This surrounding subchondral bone may be roughened to enhancetissue ingrowth or implant adhesion. The final geometry of the implantmay be determined by a dam or mold that is placed on the joint at thetime the material is implanted, when the implant is installed using anin situ cured technique (in the manner shown in FIGS. 1 and 4 ofApplicant's provisional parent application).

[0100] For pre-made material formed at the surgical site within a mold,various forms of stabilization could be used, including anchor points ortitanium screws. Alternatively, the pre-made material could be made offsite to the specs developed from imaging of the patient's joint surface.In a third embodiment, multiple sizes could be made off site and theselection of the appropriate implant size could be chosen at the time ofsurgery. Two alternatives shown in FIG. 2 of the parent provisionalapplication include a single segment that can be installed through aportal or a series of segments that can be installed through a portaland locked together once inside the joint. They would be placedsequentially and then anchored to the bone by anchor points cut in thebone or by screws or tissue ingrowth. Finally, a robot, a jag or othercutting fixture could be used to prepare the bony surface for thepre-made implant to a fixed geometry of the anchor point.

[0101] Both the preformed component(s) and flowable biomaterial, ifused, can be prepared from any suitable material. Typically, thematerials include polymeric materials, having an optimal combination ofsuch properties as biocompatibility, physical strength and durability,and compatibility with other components (and/or biomaterials) used inthe assembly of a final composite. Examples of suitable materials foruse in preparing the preformed component(s) may be the same or differentfrom the in situ curing biomaterial, and include polyurethanes,polyethylenes, polypropylenes, Dacrons, polyureas, hydrogels, metals,ceramics, epoxies, polysiloxanes, polyacrylates, as well as biopolymers,such as collagen or collagen-based materials or the like andcombinations thereof.

[0102] Examples of suitable materials for use in preparing the flowablebiomaterial, if used, include polyurethanes, polyureas, hydrogels,epoxies, polysiloxanes, polyacrylates, and combinations thereof.

[0103] In a presently preferred embodiment, the preformed component(s)and the flowable biomaterial, if included, each comprise a biocompatiblepolyurethane. The same or different polyurethane formulations can beused to form both the preformed component(s), e.g., by an injectionmolding technique, as well as for the flowable biomaterial, if present.

[0104] Suitable polyurethanes for use as either the preformed componentor biomaterial can be prepared by combining: (1) a quasi-prepolymercomponent comprising the reaction product of one or more polyols, andone or more diisocyanates, and optionally, one or more hydrophobicadditives, and (2) a curative component comprising one or more polyols,one or more chain extenders, one or more catalysts, and optionally,other ingredients such as an antioxidant, and hydrophobic additive.

[0105] In the embodiment in which an in situ curing polymer is used, thepresent invention preferably provides a biomaterial in the form of acurable polyurethane composition comprising a plurality of parts capableof being mixed at the time of use in order to provide a flowablecomposition and initiate cure, the parts including: (1) aquasi-prepolymer component comprising the reaction product of one ormore polyols, and one or more diisocyanates, optionally, one or morehydrophobic additives, and (2) a curative component comprising one ormore polyols, one or more chain extenders, one or more catalysts, andoptionally, other ingredients such as an antioxidant, hydrophobicadditive and dye. Upon mixing, the composition is sufficiently flowableto permit it to be delivered to the body, and there be fully cured underphysiological conditions. Preferably, the component parts are themselvesflowable, or can be rendered flowable, in order to facilitate theirmixing and use.

[0106] The flowable biomaterial used in this invention preferablyincludes polyurethane prepolymer components that react either ex vivo orin situ to form solid polyurethane (“PU”). The formed PU, in turn,includes both hard and soft segments. The hard segments are typicallycomprised of stiffer oligourethane units formed from diisocyanate andchain extender, while the soft segments are typically comprised of oneor more flexible polyol units. These two types of segments willgenerally phase separate to form hard and soft segment domains, sincethey tend to be incompatible with one another. Those skilled in therelevant art, given the present teaching, will appreciate the manner inwhich the relative amounts of the hard and soft segments in the formedpolyurethane, as well as the degree of phase segregation, can have asignificant impact on the final physical and mechanical properties ofthe polymer. Those skilled in the art will, in turn, appreciate themanner in which such polymer compositions can be manipulated to producecured and curing polymers with desired combination of properties withinthe scope of this invention.

[0107] The hard segments of the polymer can be formed by a reactionbetween the diisocyanate or multifunctional isocyanate and chainextender. Some examples of suitable isocyanates for preparation of thehard segment of this invention include aromatic diisocyanates and theirpolymeric form or mixtures of isomers or combinations thereof, such astoluene diisocyanates, naphthalene diisocyanates, phenylenediisocyanates, xylylene diisocyanates, and diphenylmethanediisocyanates, and other aromatic polyisocyanates known in the art.Other examples of suitable polyisocyanates for preparation of the hardsegment of this invention include aliphatic and cycloaliphaticisocyanates and their polymers or mixtures or combinations thereof, suchas cyclohexane diisocyanates, cyclohexyl-bis methylene diisocyanates,isophorone diisocyanates and hexamethylene diisocyanates and otheraliphatic polyisocyanates. Combinations of aromatic and aliphatic orarylakyl diisocyanates can also be used.

[0108] The isocyanate component can be provided in any suitable form,examples of which include 2,4′-diphenylmethane diisocyanate,4,4′-diphenylmethane diisocyanate, and mixtures or combinations of theseisomers, optionally together with small quantities of2,2′-diphenylmethane diisocyanate (typical of commercially availablediphenylmethane diisocyanates). Other examples include aromaticpolyisocyanates and their mixtures or combinations, such as are derivedfrom phosgenation of the condensation product of aniline andformaldehyde. It is suitable to use an isocyanate that has lowvolatility, such as diphenylmethane diisocyanate, rather than morevolatile materials such as toluene diisocyanate. An example of aparticularly suitable isocyanate component is the 4,4′-diphenylmethanediisocyanate (“MDI”). Alternatively, it can be provided in liquid formas a combination of 2,2′-, 2,4′- and 4,4′-isomers of MDI. In a preferredembodiment, the isocyanate is MDI and even more preferably4,4′-diphenylmethane diisocyanate.

[0109] Some examples of chain extenders for preparation of the hardsegment of this invention include, but are not limited, to short chaindiols or triols and their mixtures or combinations thereof, such as1,4-butane diol, 2-methyl-1,3-propane diol, 1,3-propane-diol ethyleneglycol, diethylene glycol, glycerol, cyclohexane dimethanol, triethanolamine, and methyldiethanol amine. Other examples of chain extenders forpreparation of the hard segment of this invention include, but are notlimited to, short chain diamines and their mixtures or combinationsthereof, such as dianiline, toluene diamine, cyclohexyl diamine, andother short chain diamines known in the art.

[0110] The soft segment consists of urethane terminated polyol moieties,which are formed by a reaction between the polyisocyanate ordiisocyanate or polymeric diisocyanate and polyol. Examples of suitablediisocyanates are denoted above. Some examples of polyols forpreparation of the soft segment of this invention include but are notlimited to polyalkylene oxide ethers derived form the condensation ofalkylene oxides (e.g. ethylene oxide, propylene oxide, and blendsthereof), as well as tetrahyrofuran based polytetramethylene etherglycols, polycaprolactone diols, polycarbonate diols and polyester diolsand combinations thereof. In a preferred embodiment, the polyols arepolytetrahydrofuran polyols (“PTHF”), also known as polytetramethyleneoxide (“PTMO”) or polytetramethylene ether glycols (“PTMEG”). Even morepreferably, the use of two or more of PTMO diols with differentmolecular weights selected from the commercially available groupconsisting of 250, 650,1000, 1400, 1800, 2000 and 2900.

[0111] Two or more PTMO diols of different molecular weight can be usedas a blend or separately, and in an independent fashion as between thedifferent parts of the two part system. The solidificationtemperature(s) of PTMO diols is generally proportional to theirmolecular weights. The compatibility of the PTMO diols with such chainextenders as 1,4-butanediol is generally in the reverse proportion tomolecular weight of the diol(s). Therefore the incorporation of the lowmolecular weight PTMO diols in the “curative” (part B) component, andhigher molecular weight PTMO diols in the prepolymer (part A) component,can provide a two-part system that can be used at relatively lowtemperature. In turn, good compatibility of the low molecular weightPTMO diols with such chain extenders as 1,4-butanediol permits thepreparation of two part systems with higher (prepolymer to curative)volume ratio. Amine terminated polyethers and/or polycarbonate-baseddiols can also be used for building of the soft segment.

[0112] The PU can be chemically crosslinked, e.g., by the addition ofmultifunctional or branched OH-terminated crosslinking agents or chainextenders, or multifunctional isocyanates. Some examples of suitablecrosslinking agents include, but are not limited to, trimethylol propane(“TMP”), glycerol, hydroxyl terminated polybutadienes, hydroxylterminated polybutadienes (HOPB), trimer alcohols, Castor oilpolyethyleneoxide (PEO), polypropyleneoxide (PPO) and PEO-PPO triols. Ina preferred embodiment, HOPB is used as the crosslinking agent.

[0113] This chemical crosslinking augments the physical or “virtual”crosslinking of the polymer by hard segment domains that are in theglassy state at the temperature of the application. The optimal level ofchemical cross-linking improves the compression set of the material,reduces the amount of the extractable components, and improves thebiodurability of the PU. This can be particularly useful in relativelysoft polyurethanes, such as those suitable for the repair of damagedcartilage. Reinforcement by virtual cross-links alone may not generatesufficient strength for in vivo performance in certain applications.Additional cross-linking from the soft segment, potentially generated bythe use of higher functional polyols can be used to provide stiffer andless elastomeric materials. In this manner a balancing of hard and softsegments, and their relative contributions to overall properties can beachieved.

[0114] Additionally, a polymer system of the present inventionpreferably contains at least one or more, biocompatible catalysts thatcan assist in controlling the curing process, including the followingperiods: (1) the induction period, and (2) the curing period of thebiomaterial. Together these two periods, including their absolute andrelative lengths, and the rate of acceleration or cure within eachperiod, determines the cure kinetics or profile for the composition.Some examples of suitable catalysts for preparation of the formed PU ofthis invention include, but are not limited to, tin and tertiary aminecompounds or combinations thereof such as dibutyl tin dilaurate, and tinor mixed tin catalysts including those available under the tradenames“Cotin 222”, “Formrez UL-22” (Witco), “dabco” (a triethylene diaminefrom Sigma-Aldrich), stannous octanoate, trimethyl amine, and triethylamine. In a preferred embodiment, the catalyst is Formrez UL-22 (Witco).In an alternative preferred embodiment, the catalyst is a combinationCotin 222 (CasChem) and dabco (Sigma-Aldrich).

[0115] The in vivo and ex vivo cured polyurethanes of this invention canbe formed by the reaction of two parts. Part I of which (alternativelyreferred to as Part A) includes a di- or multifunctional isocyanate orquasi-prepolymer which is the reaction product of one or moreOH-terminated components, and one or more isocyanates. Part II of thepolyurethane (alternatively referred to as Part B herein) is a curativecomponent that includes of one or more chain extenders and one or morepolyols, and one or more catalysts, and other additives such asantioxidants and dyes. For a suitable formed PU, the stoichiometrybetween Parts I (quasiprepolymer) and II (curative component), expressedin terms of NCO:OH molar ratio of the isocyanate terminated pre-polymer(Part I) and the curative component (Part II) is preferably within therange of about 0.8 to 1.0 to 1.2 to 1.0, and more preferably from about0.9 to 1 to about 1.1 to 1.0.

[0116] Optionally, a reactive polymer additive can be included and isselected from the group consisting of hydroxyl- or amine-terminatedcompounds selected from the group consisting of poybutadiene,polyisoprene, polyisobutylene, silicones, polyethylene-propylenediene,copolymers of butadiene with acryolnitrile, copolymers of butadiene withstyrene, copolymers of isoprene with acrylonitrile, copolymers ofisoprene with styrene, and mixtures of the above.

[0117] Suitable compositions for use in the present invention are thosepolymeric materials that provide an optimal combination of propertiesrelating to their manufacture, application, and in vivo use. In theuncured state, such properties include component miscibility orcompatibility, processability, and the ability to be adequatelysterilized or aseptically processed and stored. In the course ofapplying such compositions, suitable materials exhibit an optimalcombination of such properties as flowability, moldability, and in vivocurability. In the cured state, suitable compositions exhibit an optimalcombination of such properties as strength (e.g., tensile andcompressive), modulus, biocompatibility and biostability.

[0118] When cured, the compositions demonstrate an optimal combinationof properties, particularly in terms of their conformational stabilityand retention of physical shape, dissolution stability,biocompatibility, and physical performance, as well mechanicalproperties such as load-bearing strength, tensile strength, shearstrength, shear fatigue resistance, impact absorption, wear resistance,and surface abrasion resistance. Such performance can be evaluated usingprocedures commonly accepted for the evaluation of natural tissue andjoints, as well as the evaluation of materials and polymers in general.In particular, a preferred composition, in its cured form, exhibitsmechanical properties that approximate or exceed those of the naturaltissue it is intended to provide or replace.

[0119] To achieve these desirable uncured and delivery properties, a“polymer system”, as used herein refers to the component or componentsused to prepare a polymeric composition of the present invention. In apreferred embodiment, a polymer system comprises the componentsnecessary to form two parts: Part I being an NCO terminated pre-polymer(optionally referred to as an “isocyanate quasi-polymer”). Thequasi-polymer of Part I typically includes a polyol component,optionally in combination with a hydrophobic additive component, and anexcess of an isocyanate component. Part II of the two component systemcan include one long-chain polyols, chain extenders and/orcross-linkers, together with other ingredients (e.g., catalysts,stabilizers, plasticizers, antioxidants, dyes and the like). Suchadjuvants or ingredients can be added to or combined with any othercomponent thereof either prior to or at the time of mixing, delivery,and/or curing.

[0120] In a particularly preferred embodiment, a polymer system of thisinvention is provided as a plurality of component parts and employs oneor more catalysts. The component parts, including catalyst, can be mixedto initiate cure, and then delivered, set and fully cured underconditions (e.g., time and exotherm) sufficient for its desired purpose.Upon the completion of cure, the resultant composition provides anoptimal combination of properties for use in repairing or replacinginjured or damaged tissue. In a particularly preferred embodiment, theformulation provides an optimal combination of such properties ascompatibility and stability of the biomaterial parts, ex vivo or in situcure capability and characteristics (e.g., extractable levels,biocompatibility, thermal/mechanical properties), mechanical properties(e.g., tensile, tear and fatigue properties), and biostability.

[0121] The volume ratio of the parts can also be used to improve andaffect the uncured and curing properties Compositions having two or moreparts, are preferred. Where two parts are used, the relative volumes canrange, for instance, from 1:10 to 10:1 (quasi-prepolymer to curativecomponents, based on volume). A presently preferred range is between 2:1and 1:2. As those skilled in the art will appreciate, given the presentdescription, the optimal volume ratio is largely determined by thecompatibility and the stability of part A and B.

[0122] In choosing an optimal volume ratio for a given formulation,those skilled in the art, given the present description, will appreciatethe manner in which the following considerations can be addressed. Theviscosity of the reactive parts, at the temperature used for eitherinjection-molding preformed components, or for in situ cure, shouldprovide an acceptable degree of mixing and flow rate, without causingmechanical failure of any component of the delivery system includingcartridge, static mixer, gun and other components.

[0123] Preferably, the biomaterial is sufficiently flowable to permit itto be delivered (e.g., injected) into the mold or tissue site. Thecomposition of both reactive parts must be such that these parts arehomogeneous and phase stable in the temperature range of theapplication. Generally, the maximum temperature of the reaction exothermis proportional to the concentration of the reactive groups in the mixedpolymer. A high concentration of the reactive groups might evolve toohigh reaction exothermal energy and therefore cause thermal damage tothe surrounding tissues. The reactive parts will preferably remainsubstantially liquid in form during mixing.

[0124] A desired and stable volume ratio of the components can beachieved in any suitable manner, e.g., by the use of dual-compartmentcartridges with constant volume ratio or by using the injectors withdelivery rates independently variable for each component.

[0125] Compatibility of the composition can also be affected (andimproved) in other ways as well, e.g., by pre-heating the componentsprior to polymer application. To enhance the homogeneity of thecomponents, the components of a preferred composition of this inventionare preferably preheated before mixing and delivery, e.g., by heating toabout 40 C, more preferably about 60 C, to about 80 C for about 2 toabout 6 hours prior to use or for the time necessary for completemelting and forming of the member. Preferably, the composition parts arecooled back to about 35 C to 37 C before use in injection.

[0126] Fully cured polymeric (e.g., polyurethane) biomaterials suitablefor use in forming components of this invention provide an optimalcombination of such properties as creep and abrasion resistance.Preferably, for instance, the biomaterial provides DIN abrasion valuesof less than about 100 mm³, more preferably less than about 80 mm³ andmost preferably less than about 60 mm³, as determined by ASTM TestMethod D5963-96 (“Standard Test Method for Rubber Property AbrasionResistance Rotary Drum Abrader”).

What is claimed is:
 1. A system for the creation or modification of an orthopedic joint within a mammalian body, the system comprising one or more partially or fully preformed polymeric components, adapted to be inserted and positioned at a joint site to provide an implant having at least one major surface in apposition to supporting bone, and at least a second major surface in apposition to opposing bone, wherein the implant is a knee implant and provides a first major surface adapted to be positioned upon and congruent with the tibial surface of the knee, and a second major surface adapted to be positioned against the femoral condyle of the knee, and wherein the second major surface is provided with a femoral glide path to facilitate its performance in situ, the glide path being in the form of a generally central depression, the implant further comprising one or more tibial projections adapted to extend distally over the rim of the tibial plateau in order to improve fixation in situ.
 2. A system according to claim 1 wherein the polymeric components are provided in the form of a single preformed component comprising a biomaterial partially or completely cured in an ex vivo mold.
 3. A system according to claim 1 wherein the tibial projection(s) are adapted to catch the posterior portion of the tibial plateau by extending over the rim of the tibial plateau distally, and the preformed component has dimensions on the order of between about 30 to about 60 mm in the anterior-posterior dimension, between about 20 mm to about 40 mm in the medial-lateral dimension, and a maximum thickness, at the posterior lip, of between about 8 mm and about 20 mm, or about 3 mm to about 10 mm greater than the thickness of the implant at the center.
 4. A system according to claim 1 wherein the implant further comprises at least one ancillary component integrated into, and partially extending from, the implant to provide anterior fixation.
 5. A system according to claim 4 wherein the ancillary component comprises one or more protrusions adapted to be attached to either soft tissue and/or bone at the joint site to improve fixation.
 6. A system according to claim 5 wherein the protrusions are adapted to be integrated into the preformed component during an ex vivo molding process.
 7. A system according to claim 6 wherein the protrusions are comprised of sutures and/or fibrous biomaterials integrally formed with the preformed component itself.
 8. A system according to claim 1 further comprising one or more separate components for securing the implant to the joint site, selected from the group consisting of adhesives, sutures, pins, staples, screws, and combinations thereof.
 9. A system according to claim 2 wherein a plurality of preformed components are provided in a corresponding plurality or range of styles and sizes for selection and use in the surgical field.
 10. A system according to claim 1 wherein one or more of the polymeric components comprise a polyurethane.
 11. A system according to claim 10 wherein the polyurethane is prepared from polyisocyanate(s), short and long chain polyols, and optionally including one or more ingredients selected from the group hydrophobic additive(s), tin and/or amine catalyst(s), and antioxidant(s).
 12. A system according to claim 10 wherein the polyurethane comprises aromatic polyisocyanates, PTMO's, and short chain diols.
 13. A system according to claim 11 wherein the hydrophobic additive comprises hydroxyl-terminated polybutadiene, and the tin and/or amine catalyst(s) are adapted to promote the isocyanate-hydroxyl reaction preferentially and are selected from the group consisting of UL22, Cotin 222, 1,4-diazabicyclo[2.2.2]octane (dabco), and dibutyltin dilaurate (DBTDL), and combinations thereof.
 14. A system according to claim 10 wherein the polyurethane comprises an isocyanate selected from the group consisting of aromatic, aliphatic and arylakyl diisocyanates, and combinations thereof.
 15. A system according to claim 14 wherein the isocyanate is selected from the group consisting of toluene diisocyanates, naphthalene diisocyanates, phenylene diisocyanates, xylylene diisocyanates, diphenylmethane diisocyanates, cyclohexane diisocyanates, cyclohexyl-bis methylene diisocyanates, isophorone diisocyanates and hexamethylene diisocyanate
 16. A system according to claim 1, wherein the polymeric component comprises one or more surfaces having attached thereto a biologically active agent selected from the group cytokines, growth factors, autologous growth factors, hydroxyapatite, collagen, and combinations thereof.
 17. A system according to claim 1 wherein the surface of the polymeric component is provided or modified with reactive groups to promote tissue adhesion.
 18. A system according to claim 17 wherein the reactive groups are provided by the polymers used to fabricate the polymeric component, and are selected from amines, hydroxyl groups, or other reactive or hydrogen bonding functionalities.
 19. A system according to claim 1 wherein the glide path is in the form of a generally central oval depression about 0.5 mm to about 5 mm deep at its lowest point and about 20 mm to about 50 mm in length by 10 mm to 30 mm in width.
 20. A system according to claim 2 wherein the component is preformed in a mold having an anterior cup edge that is substantially perpendicular to the plane of the cup itself, and a posterior mesial edge that is tapered to accommodate the corresponding shape of the tibial spine.
 21. A system according to claim 20 wherein the mold is adapted to permit control of sizing, conformance to the joint site, implant thickness and angular correction.
 22. A system according to claim 1 further comprising a patella-femoral joint form suitable adapted to be formed to, and held against, the femoral bone surface, in order to permit the delivery of curable biopolymer between the form and the bone.
 23. A system according to claim 1 wherein the polymeric components are provided in the form of a single preformed component comprising a polyurethane partially or completely cured in an ex vivo mold, and wherein the implant that comprises the preformed component further comprises at least one ancillary component integrated into, and partially extending from, the implant to provide anterior fixation.
 24. A system according to claim 23 wherein the polyurethane comprises an isocyanate selected from the group consisting of aromatic, aliphatic and arylakyl diisocyanates, and combinations thereof.
 25. A system according to claim 24 wherein the isocyanate is selected from the group consisting of toluene diisocyanates, naphthalene diisocyanates, phenylene diisocyanates, xylylene diisocyanates, diphenylmethane diisocyanates, cyclohexane diisocyanates, cyclohexyl-bis methylene diisocyanates, isophorone diisocyanates and hexamethylene diisocyanate
 26. A system according to claim 23, wherein the polymeric component comprises one or more surfaces having attached thereto a biologically active agent selected from the group cytokines, growth factors, autologous growth factors, hydroxyapatite, collagen, and combinations thereof.
 27. A system according to claim 3 wherein the surface of the polymeric component is provided or modified with reactive groups to promote tissue adhesion.
 28. A system according to claim 3 wherein the glide path is in the form of a generally central oval depression about 0.5 mm to about 5 mm deep at its lowest point and about 20 mm to about 50 mm in length by 10 mm to 30 mm in width.
 29. A system according to claim 15 wherein the glide path is in the form of a generally central oval depression about 0.5 mm to about 5 mm deep at its lowest point and about 20 mm to about 50 mm in length by 10 mm to 30 mm in width.
 30. A system according to claim 23 wherein the biomaterial comprises a polyurethane and the glide path is in the form of a generally central oval depression about 0.5 mm to about 5 mm deep at its lowest point and about 20 mm to about 50 mm in length by 10 mm to 30 mm in width. 